Controlling light absorption of graphene at critical coupling through magnetic dipole quasi-bound states in the continuum resonance

TL;DR

This paper presents a method to control light absorption in graphene using quasi-BIC resonances, enabling tunable high absorption for advanced photonic devices by engineering radiation and dissipation rates.

Contribution

It introduces a novel approach linking bound states in the continuum with radiation engineering to achieve tunable light absorption in graphene-based systems.

Findings

Maximum absorption of 0.5 achieved at critical coupling.

Absorption bandwidth tunable from 0.9 nm to 94 nm.

Control over absorption via metasurface asymmetry, Fermi level, and layer number.

Abstract

Enhancing the light-matter interaction in two-dimensional (2D) materials with high-$Q$ resonances in photonic structures has boosted the development of optical and photonic devices. Herein, we intend to build a bridge between the radiation engineering and the bound states in the continuum (BIC), and present a general method to control light absorption at critical coupling through the quasi-BIC resonance. In a single-mode two-port system composed of graphene coupled with silicon nanodisk metasurfaces, the maximum absorption of 0.5 can be achieved when the radiation rate of the magnetic dipole resonance equals to the dissipate loss rate of graphene. Furthermore, the absorption bandwidth can be adjusted more than two orders of magnitude from 0.9 nm to 94 nm by simultaneously changing the asymmetric parameter of metasurfaces, the Fermi level and the layer number of graphene. This work reveals out the essential role of BIC in radiation engineering and provides promising strategies in controlling light absorption of 2D materials for the next-generation optical and photonic devices, e.g., light emitters, detectors, modulators, and sensors.